A walk-behind lawnmower is provided with a housing, which is provided with front wheels and rear wheels and is open at the bottom; a blade that is rotatably housed within the housing; and an operating handle for the operator to steer while walking. This walk-behind lawnmower can proceed while using the blade to cut grass and is appropriate for cutting grass in household yards or other narrow areas.
A walk-behind lawnmower of such description is provided with a height-adjusting mechanism that is capable of adjusting the height of the housing and the blade in relation to the ground in order to adjust the mowing height. In the height-adjusting mechanism, a lock-release operating member is operated by hand in order to lock in the adjusted height. There are two formats for positioning the lock-release operating member in relation to the housing. In the first positioning format, the lock-release operating member is positioned on a rear part of the housing (in front of the grass bag in which the grass cut by the blade is stored). In the second positioning format, the lock-release operating member is positioned on a lateral part of the housing. The operator need not reach their hand into the interior of the walk-behind lawnmower in the second positioning format, and therefore the adjustment operation is simple, and this format is widely used. An example of a walk-behind lawnmower in which the second positioning format is employed is disclosed in Japanese Patent No. 2599658.
The height-adjusting mechanism of a walk-behind lawnmower disclosed in Japanese Patent No. 2599658 is provided with a front wheel-supporting member and a rear wheel-supporting member that are linked to the front and rear of the housing so as to allow up-and-down swinging; a height-adjusting plate that is linked to the upper part of the housing so as to allow up-and-down swinging; a front rod and a rear rod that convey the swinging motion of the height-adjusting plate to the front and rear wheel-supporting members; and a locking mechanism for restricting the swinging motion of the height-adjusting plate. The front wheel-supporting member supports the front wheels, and the rear wheel-supporting member supports the rear wheels.
The locking mechanism is composed of a plurality of locking grooves that is formed on the height-adjusting plate; a locking pin that can selectively interlock with one of the locking grooves; and an operating knob (lock-release operating member) that is operated so as to insert and retract the locking pin in relation to one of the locking grooves. The operating knob is provided to the housing in the vicinity of the left lateral part, and is capable of swinging up and down.
When the operator uses the finger of one hand to swing the operating knob upward, the locking pin separates from the locking groove, and the height-adjusting plate can therefore swing up and down. The operator uses the other hand to grasp the operating handle for steering the lawnmower and move the handle up or down while holding the operating knob in the same position, whereby the height of the housing and the blade can be adjusted. When the hand is taken away from the operating knob after adjustment, the operating knob automatically returns to the original position, whereby swinging of the height-adjusting plate is restricted.
However, in the height-adjusting mechanism disclosed in Japanese Patent No. 2599658, the operator must use one hand to grasp the operating handle for steering the lawnmower, and move the handle up or down while using the other hand to operate the operating knob. In other words, two members must be operated respectively using two hands. There is room for further improvement in increasing the operability of the height-adjusting mechanism.